<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<style>
#nonexist { background: url(ref/green.bmp); }
</style>
<style>
@media print {
  #nonexist { color: green; }
}
</style>
<style>
@keyframes demo {
  from { transform: translateX(-5px); }
  to { transform: translateX(40px); }
}
#nonexist { animation: demo 3s linear infinite; }
</style>
<style>
@supports (--myvar: green) {
  :root {
    --myvar: green;
  }
  #nonexist {
    color: var(--myvar);
  }
}
</style>
<style>
@namespace svg url(http://www.w3.org/2000/svg);
|nonexist text { fill: blue; }
svg|nonexist text { fill: blue; }
*|nonexist text { fill: blue; }
</style>
<style>
/* unsupported rules */
#nonexist {
  *background: url(ref/unsupported-1.bmp); /* IE7 */
  _background: url(ref/unsupported-2.bmp); /* IE6 */
  -o-background: url(ref/unsupported-3.bmp); /* vandor prefix */
  unknown: url(ref/unsupported-4.bmp); /* unknown */
}
</style>
</body>
</html>
